Author 'Daniel78' (Id 197861 ) : On the canal Saint-Martin, on the covered part, there are public squares, etc. The cone mesh serves as the vent for the channel. It is about 5/6 metres below. The squares are well-equipped with games and flower beds, but unfortunately badly frequented by many homeless and this is very unpleasant because by the time they occupy the passage, and more... lots of smells of urine !... and yet, I've never seen so many toilets in Paris along the route of the canal Saint-Martin !